1. Field of the Invention
The present invention relates to an image forming apparatus for developing with a developer and recording an electrostatic image on an image bearing body corresponding to an image to be recorded, on a recording material such as paper.
2. Related Background Art
Conventional types of many image forming apparatuses using an electrophotography method or an electrostatic recording method have been proposed. A schematic structure and the operation of such apparatuses are explained using FIG. 9.
When a copy start signal is input to the image forming apparatus shown in FIG. 9, a photosensitive drum 1 is charged as an image bearing body to be a predetermined potential by a charging apparatus 3.
On the other hand, a unit 9 having a subject irradiation lamp, a short focus lens array, and a CCD sensor is scanned with respect to a original G mounted on a copy board 10 while irradiating the original, and light reflected by the surface of the original from the irradiated scanning light is imaged by the short focus lens array and made incident to the CCD sensor. The CCD sensor is structured by a light receiving portion, a transferring portion, and an output portion.
Optical signals are changed into electric charge signal in the light receiving portion, are transferred in order to the output portion in synchronous with a clock pulse in the transferring portion, and the electric charge signals are converted into electric voltage signals, amplified, and made low impedance in the output portion. The obtained analog signals are transformed into digital signals by performing a known imaging process, and are then sent to a printer portion. In the printer portion, an electrostatic latent image corresponding to the subject image is formed on the photosensitive drum 1 by scanning on-off luminary of solid state laser element triggered by the received image signal in laser exposing means 2 rotational multi-faced mirror rotating at high speed.
Next, the electrostatic latent image is developed by a developer apparatus 4 holding a two-component developer having toner particles and carrier particles and obtained on the photosensitive drum 1 as a toner image.
The toner image thus formed on the photosensitive drum 1 is electrostatically transferred onto a transfer material by a transfer apparatus 7. The transfer material is then electrostatically separated, and conveyed to a fixing apparatus 6, thermally fixed, and the image is output. The transfer apparatus 7 comprises a transfer belt 71 wrapped around a pair of rollers 72 and 73, and a transfer electrostatic blade 74 arranged on the inside of the transfer belt 71.
Recently, due to advantages such as low ozone and low electric power, a contact charging apparatus, namely an apparatus for performing charging of an object by contacting a charged member, to which a voltage is applied, to the object, has been made practical as the charging member of the photosensitive drum 1.
It is preferable to use a magnetic brush apparatus as this type of charging member because of stable charging contact.
In the magnetic brush contacting charging apparatus, changing begins by contacting conductive magnetic particles directly constrained on a magnet, or magnetically constrained on a sleeve enclosing a magnet, to a charging body to be charged while stopped or while rotating and by applying a voltage.
Further, a brush on which conductive fibers are formed (hereafter referred to as a fur brush) and a conductive rubber roller in which a conductive rubber is made into a roll shape are also preferably used as a contact charging member.
In particular, if a photosensitive body such as a normal organic photosensitive body having a surface layer on which conductive micro-particles are scattered, or an amorphous photosensitive body is used as the charging body to be charged while using this type of contact charging member, then it is possible to obtain a static charge potential on the surface of the charging body to be charged which is nearly equivalent to the direct current component of the bias applied to the contact charging member. This type of charging method focused on recently is referred to as injection charging. The injection charging of the body to be charged is performed without utilizing electric discharge developing using a corona charging apparatus, and therefore perfectly, ozone-less and low power consumption charging becomes possible provided that injection charging is used. Furthermore, in recent years, color electrophotography apparatus themselves have photosensitive bodies and developer apparatuses corresponding to each of four colors as with an image forming apparatus shown in FIG. 1 as an embodiment of the present invention, and tandem methods in which four color images are overlapped in order on a transfer material during one pass, namely during conveying the transfer material one time have been developed. This method has an advantage in that color recording may be conducted at high speed.
In addition, a cleaner-less method is employed in the tandem method color image forming apparatus having the magnetic brush charging apparatus shown in FIG. 1, in which cleaning of the remaining transfer toner on the photosensitive drum is performed by the developer apparatus 4 at the same time as developing of the electrostatic latent image, without providing a specialized cleaning apparatus.
With an image forming apparatus prepared with the above cleaner-less method, the toner remaining on the photosensitive body which was not transferred to the transferring material is collected temporarily by the magnetic brush charging apparatus 3, and is next discharged once again to the photosensitive drum after being polarized, and is collected by the developer apparatus. However, the toner flies off from the photosensitive drum to an exposure light emitting portion by a changes of electric potential distribution on the photosensitive drum caused by image exposing in the next process. A problem therefore exists in which poor copy of an image is caused by the toner thus adhering to the exposure apparatus.
In particular, in case of a tandem type method in which four stations are arranged in parallel and imaging processes are performed by each station independently, there is a problem in which a colour of station toner is mixed into a colour of toner expelled from the magnetic brush charging apparatus.
The present invention is made in view of the above stated issues, and an object of the present invention is to provide an image forming apparatus capable of suppressing toner adhesion to an exposure surface.
Another object of the present invention is to provide an image forming apparatus, comprising: a photosensitive member; image exposing means for exposing the photosensitive member in accordance with an image information, said image exposing means having a lens facing the photosensitive member; a conductive member adjacent to the lens; and voltage application means for applying a voltage to the conductive member, wherein a voltage equal to or greater than 1500 V as applied by the voltage application means.
In addition, another object of the present invention is to provide an image forming apparatus comprising: a photosensitive member; charging means for charging the photosensitive member; image exposing means for exposing the photosensitive member in accordance with an image information, said image exposing means having a lens facing the photosensitive member; a conductive member adjoining the lens; and voltage application means for applying a voltage to the conductive member; wherein the voltage application means applies a voltage to the conductive member in synchronous with a timing for voltage application to the charging means.
Additionally, another object of the present invention is to provide an image forming apparatus, comprising: a photosensitive member; image exposing means for exposing the photosensitive member in accordance with an image information, said image exposing means having a lens facing the photosensitive member; a conductive member adjoining the lens; and voltage application means for applying a voltage to the conductive member; wherein the voltage application means applies a voltage to the conductive member in synchronous a timing for driving the photosensitive member.
Another object of the present invention is to provide an image forming apparatus, comprising: a photosensitive member; image exposing means for exposing the photosensitive member in accordance with an image information, said image exposing means having a lens facing the photosensitive member; a conductive member adjoining the lens; environment detection means for detecting an environmental state; and voltage application means for applying a voltage to the conductive member; wherein the voltage application means applies a voltage to the conductive member in correspondence with output of the environmental detection means.
In addition, another object of the present invention is to provide an image forming apparatus, comprising: a photosensitive member; charging means for charging the photosensitive member; image exposing means for exposing the photosensitive member in accordance with an image information, said image exposing means having a lens facing the photosensitive member; a conductive member adjoining the lens; wherein both and portions of the conductive member in a longitudinal direction are outside of a charging region.